1. Field of the Invention
The present invention concerns a light guide, line illumination apparatus and image acquisition system, more particular, the apparatus and system used for facsimile and copying machines, a hand scanner, an optical character reader (OCR) and such.
2. Description of the Related Art
A line illumination apparatus for illuminating an object to obtain image data, for example, by image sensor has been used conventionally. The line illumination apparatus, which consists of a light source and a light guide, requires the light from the light source to illuminate an object efficiently.
A light guide used in such type of line illumination apparatus is disclosed in, for example, a Japanese Open-laid Pat. No. 163320/1996. An operation of such line illumination is shown in principle in FIG. 19.
In FIG. 19, a light guide 101a is made of transparent resin and is provided with a light emitting diode (LED) 102a as a light source at an end surface thereof. When it is used for a color image scanner, a light having exited from the LED 102a is reflected at the wall surface inside the light guide and transmitted toward the other end surface.
The transmitted light is scattered at a scattering mark 103a. The diffused light, which does not meet the condition of total reflection, of the scattered light is outputted outside through a light exit surface 113a. The scattering mark 103a is formed by means of white paint, diffusion agent added paint, or the like.
Outside the light guide is provided a reflection board 120a as shown in FIG. 20. A light scattered at the scattering mark 103a is led into the light guide 101a again when it hits the reflection board 120a even after outputted outside the light guide 101a. The reflection board 120a is formed by means of a white diffusing reflection material.
A part near the illumination area 104a of the light guide 101a is arranged to output a light outside as a light exit surface 113a. The light exiting through this light exit surface 113a illuminates the illumination area 104a via a glass board 105a. 
In this example, the light, part of which is outputted outside due to the scattering mark 103a through the light exit surface 113a of the light guide 101a, decreases in intensity by the outputted amount of light. That is, the farther the light source is distanced, the more the intensity of light attenuates gradually. In order to further improve the efficiency of obtaining the light as it goes away from the light source, it has been performed to make the illumination at the illumination area 104a uniform by increasing the density of the scattering mark 103a or by widening the mark.
In the conventional technology, however, the light scattered at the scattering mark is further reflected and scattered at the reflected board repeatedly, so that the light exiting from the light guide has a component to be transmitted in various direction. Thus, it was difficult to sufficiently hold down the unnecessary light that illuminates even an area far away from the illumination area. Therefore, it has been problems that the light emitted by the light source is difficult to be used efficiently, and that it is difficult to achieve the enough illumination without increasing the electric power consumed by the light source.
Further, raising the illumination of the illumination area near the light source could not make the illumination of the whole illumination area uniform since the light emitted by the sole light source provided at one end of the light guide illuminates the whole illumination area. It is because the light emitted by the light source illuminates the illumination area after scattered at the scattering mark and outputted outside the light guide through the light exit surface. Insufficient scattering of light near the light source of the light guide reduces the amount of light outputted through the light exit surface, which causes a shortage of the illumination.
Thus, in conventional arrangement, it could not be achieved that the whole illumination area being illuminated at the uniform illumination by raising the illumination of the illumination area near the light source, though the illumination of the illumination area away from the light source could be raised.
An object of the present invention is to provide a light guide, a line illumination apparatus and an image acquisition system, capable of efficiently illuminating the illumination area with the light emitted by the light source.
Another object of the present invention is to provide a light guide, a line illumination apparatus and an image acquisition system, capable of uniformly illuminating the whole illumination area at the sufficient illumination with a simple arrangement.
To accomplish the object described above, the present invention provides a light guide, line illumination apparatus and image acquisition system having the constructions listed below.
The first aspect of the invention, a light guide comprises a transparent member in the shape of a bar, a scattering mark configured to scatter a light transmitted inside the transparent member substantially vertical to the longitudinal direction relative to the transparent member, a reflection surface, having a curved surface, configured to reflect a light scattered at the scattering mark inside the transparent member, and a light exit surface configured to enable a light reflected at the reflection surface to exit outside the transparent member therethrough.
The second aspect of the invention, a light guide comprises a transparent member in the shape of a bar, a scattering mark configured to scatter a light transmitted inside the transparent member substantially vertical to the longitudinal direction relative to the transparent member, a reflection surface, having a curved surface, configured to reflect a light scattered at the scattering mark inside the transparent member, a first light exit surface configured to enable a light reflected at the reflection surface to exit outside the transparent member therethrough, and a second light exit surface configured to enable a light scattered at the scattering mark to exit outside of the transparent member therethrough.
The third aspect of the invention, a line illumination apparatus comprises a light guide including a transparent member in the shape of a bar, and a light source provided at the end of the light guide in the longitudinal direction relative to the light guide, wherein the light guide comprises a scattering mark configured to scatter a light transmitted inside the transparent member from the light source substantially vertical to the longitudinal direction relative to the transparent member, a reflection surface, having a curved surface, configured to reflect a light scattered at the scattering mark inside the transparent member, and a light exit surface configured to enable a light reflected at the reflection surface to exit outside the transparent member therethrough.
The fourth aspect of the invention, a line illumination apparatus comprises a light guide including a transparent member in the shape of a bar, and a light source provided at the end of the light guide in the longitudinal direction relative to the light guide wherein the light guide comprises a scattering mark configured to scatter a light transmitted inside the transparent member from the light source substantially vertical to the longitudinal direction relative to the transparent member a reflection surface, having a curved surface, configured to reflect a light scattered at the scattering mark inside the transparent member, a first light exit surface configured to enable a light reflected at the reflection surface to exit outside the transparent member therethrough, and a second light exit surface configured to enable a light scattered at the scattering mark to exit outside of the transparent member therethrough.
The fifth aspect of the invention, an image acquisition system comprises a light guide including a transparent member in the shape of a bar, a light source provided at the end of the light guide in the longitudinal direction relative to the light guide, an image forming optical device configured to form an image of a light from an illumination area illuminated by a light exiting from the light guide, and n image sensor configured to read a light of the image formed by the image forming optical device, wherein the light guide comprises a scattering mark configured to scatter a light transmitted inside the transparent member from the light source substantially vertical to the longitudinal direction relative to the transparent member, a reflection surface, having a curved surface, configured to reflect a light scattered at the scattering mark inside the transparent member, and a light exit surface configured to enable a light reflected at the reflection surface to exit outside the transparent member therethrough.
The sixth aspect of the invention, an image acquisition system comprises a light guide including a transparent member in the shape of a bar, a light source provided at the end of the light guide in the longitudinal direction relative to the light guide, an image forming optical device configured to forming an image of a light from an illumination area illuminated by a light exiting from the light guide, and an image sensor configured to read a light of the image formed by the image forming optical device, wherein the light guide comprises a scattering mark configured to scatter a light transmitted inside the transparent member from the light source substantially vertical to the longitudinal direction relative to the transparent member, a reflection surface, having a curved surface, configured to reflect a light scattered at the scattering mark inside the transparent member, a first light exit surface configured to enable a light reflected at the reflection surface to exit outside the transparent member therethrough, and a second light exit surface configured to enable a light scattered at the scattering mark to exit outside of the transparent member therethrough.
The seventh aspect of the invention, a line illumination apparatus comprises, a light guide including of a transparent member in the shape of a bar, and a light source provided at a first end of the light guide in the longitudinal direction relative to the light guide, wherein the light guide comprises a scattering mark configured to scatter a light emitted by the light source, a light exit surface configured to enable a light scattered at the scattering mark to exit outside the transparent member therethrough, and a reflection portion, provided near the first end, configured to interrupt a light, which is emitted by the light source, to be transmitted to a second end facing to the first end and for reflecting the interrupted light so as to enable the interrupted light to exit from the light exit surface located near the light source.
The eighth aspect of the invention, an image acquisition system comprises, a light guide including a transparent member in the shape of a bar, a light source provided at the end of the light guide in the longitudinal direction relative to the light guide, an image forming optical device configured to form an image of a light from an illumination area illuminated by a light exiting from the light guide, and an image sensor configured to read a light of the image formed by the image forming optical device, wherein the light guide comprises a scattering mark configured to scatter a light emitted by the light source, a light exit surface configured to enable a light scattered at the scattering mark to exit outside the light guide therethrough, and a reflection portion, provided near the first end, configured to interrupt a light, which is emitted by the light source, to be transmitted to a second end facing to the first end and for reflecting the interrupted light so as to enable the interrupted light to exit from the light exit surface located near the light source.
The ninth aspect of the invention, a line illumination apparatus comprises a light guide including of a transparent member in the shape of a bar, and a plurality of light sources provided along the longitudinal direction relative to the transparent member, wherein the light guide comprises a reflection surface, having a curved surface, configured to reflect a light emitted by the light source inside the transparent member, and a light exit surface configured to enable a light reflected at the reflection surface to exit outside the transparent member therethrough.
The tenth aspect of the invention, an image acquisition system comprises a light guide including of a transparent member in the shape of a bar, a plurality of light sources provided along the longitudinal direction relative to the light guide, an image forming optical device configured to form an image of a light from an illumination area illuminated by a light exiting from the light guide, and an image sensor configured to read a light of the image formed by the image forming optical device, wherein the light guide comprises a reflection surface, having a curved surface, configured to reflect a light emitted by the light source inside the transparent member, and a light exit surface configured to enable a light reflected at the reflection surface to exit outside the transparent member therethrough.
According to the present invention, the light scattered at the scattering mark is effectively led to the illumination area, so that a line illumination apparatus with a simple arrangement and high efficiency can be achieved.
It is also available to provide a compact line illumination apparatus or an image acquisition system at a low cost by adopting the light guide according to the present invention.
In addition, according to the present invention, the reflection of the light emitted by the light source at a reflection portion of the light guide can uniform the illumination of the whole illumination area illuminated by the reflected light.